I asked almost the same question about Coumadin. The answer seems to be thatwhen the Clinical Trials are conducted the drug companies and FDA do not test drugs for effects on exercise (or safety during exercise). The common tests are for stuff like whether the drug makes your hair fall out, causes diarrhea, fever, rash, etc. From my own totally unscientific study I see no discernible difference between Coumadin or Lovenox while exercising. I do not see either of them as being performance enhancing or performance degrading to any great degree. I have not heard of any athletes being reprimanded for using either drug (and I have not heard of athletes lining up to use them either). I did a cursory check of a list of banned substances and neither drug appears to be prohibited for athletes. Given the lack of scientific data I'd recommend go ahead and exercise with caution; e.g., recommend that you wear a heart rate monitor while exercising.